Kinetics of Etching of Dislocations in Ferroelectric Ammonium Hydrogen Tartrate Single Crystals

Ferroelectric crystals of Ammonium Hydrogen Tartrate (AHT) have been synthesised using the controlled reaction between NH₄Cl and (CHOHCOOH)₂ by diffusion process in silica gel medium. (010) cleavages of AHT crystals have been etched in 1.0 M and 1.5 M solutions of SrCl₂ solution. The lateral and normal velocities of the growth of pits were measured at different temperatures. The time dependence of the growth of the pit dimensions is found to be linear, whereas the temperature dependence of the growth of pits is found to be exponential, viz. \documentclass{article}\pagestyle{empty}\begin{document}$ \[V = A\,\exp \left({\frac{E}{{kT}}} \right)\] $\end{document}. The dissolution parameters, e.g. the activation energies and the pre-exponential factors for dissolution along the surface and along the dislocation lines have been computed. It is observed that the activation energy (E₁) of dissolution along [001] direction is found to be greater than the activation energy (E_b) along [100] direction and the implications are discussed.     

The Thermal Etching of GaP

The thermal decomposition and etching of GaP have been investigated. The {111} GaP surfaces were treated in 10⁻²—10⁻⁵ torr vacuum, and in hydrogen and argon atmosphere, in a temperature range of 900—1300 K. Under the different experimental conditions the etched surfaces show different morphological characteristics and polar properties, from which the suitable range for thermal etching or polishing can be choosen. All experiments show that the evaporation mechanism in vacuum and argon is similar, but in hydrogen the process is different.     

Plasma Etching of Niobium-SiOx Layers

CF₄-plasma etching of niobium and SiO_x layers has been investigated in a r.f. diode reactor. Etch rates increase linearly with increasing power density and also increase with pressure. The etch rate ratio can be changed using different etch gases or operating in different plasma modes (PE or IEPE). Changing from the ion enhanced plasma etching mode (IEPE) to plasma etching mode (PE) the etch rate ratio is changing by an factor of ten. On the basis of etch rate dependences on process parameters and thermodynamic data it has been suggested the generation of flourine radicals as the rate limiting step. A general etching model has been proposed, which explains qualitavelty and quantitatively (on account of data from literature) the measured results.     

Precipitation-induced Dislocations in Crystals of NaCl:Ni

Using the decoration technique, the dislocation structure has been observed in regions localized near precipitates in nickel-doped NaCl crystals. The results are interpreted in terms of the stress-operated mechanism for the generation of prismatic dislocations by the precipitates. Normally only two of twelve possible slip directions operate for 〈110〉 rods. This is accounted for in terms of the climb and disappearance of dislocation loops corresponding to the other directions. {100} plates produce loops spreading along for 〈110〉 directions.     

低位错ZnSe单晶的生长

采用化学气相输运法(CVT)在适合的温度和I2含量的条件下,生长出了25mm×3mm的ZnSe单晶,位错密度为6.5×103个/cm2.对ZnSe单晶进行光学性能分析,在10.6μm处的透过率超过70;,在10.6μm处的吸收系数为7.72×10-4/cm.     

碳化硅单晶位错研究进展

SiC作为代表性的第三代半导体材料,具有优异的物理化学性能。随着材料及应用的发展,SiC衬底在航天电源、电动汽车、智能电网、轨道交通、工业电机等领域的应用日益重要。相比第一代半导体材料如Si和第二代半导体材料如GaAs而言,SiC衬底质量还有很大的改善空间,是现阶段研发和产业的热点。其中SiC单晶缺陷,特别是一维位错缺陷的检测和降低,是近10年内重要的研究内容。本文重点对SiC中位错的形成原因、位错检测技术、位错密度降低方法及近年来SiC单晶中位错的优化水平进行总结归纳,并提出了SiC需要继续突破和发展的方向。     

Method of Evaluating Geometrical-Statistical Parameters of the Interaction between Dislocations and Point Obstacles from Electron Micrographs

Electron micrographs of MgO crystals deformed in the HVEM show screw dislocations of curly shape. The dislocations are pinned at localized obstacles and bow out between them. The paper describes a measuring procedure for the geometrical interaction parameters between the dislocations and the obstacles. Such are the effective stress, the obstacle distance and the force acting on the obstacles. The procedure consists in a graphical fit of loops calculated by the DE WITT-KOEHLER line tension model to the observed dislocation segments.     

近红外半导体材料HgInTe的缺陷腐蚀

研究了HgInTe的腐蚀工艺,探索出一种适合于HgInTe的腐蚀液,并对腐蚀原理做了分析.利用该腐蚀液对HgInTe晶体内部的缺陷种类和分布进行了研究.结果表明,垂直轴向切割的HgInTe晶片腐蚀后的位错蚀坑呈近等腰三角形.在本实验条件下,位错蚀坑密度EPD(etch-pit density)约在105/cm2数量级.HgInTe晶体中的位错墙主要以边重叠和角重叠两种方式排列而成.HgInTe中存在少量由内应力引起的微裂纹.该腐蚀液能有效地显示HgInTe晶体不同晶面的多种缺陷,腐蚀效果较好.     

Dislocations of salol crystals grown by the Czochralski method

Crystals of salol were grown by the Czochralski method in three different pulling directions to examine the crystallographic orientation effect of the seed. They were characterized by the etch pit method and X-ray projection topography. It was found that the dislocation density was 2 × 10³−1 × 10⁴/cm² and that the configuration of dislocations was straight. The running directions of dislocations strongly depend on the pulling directions; i.e., [11 0] and [1 10] for the crystal grown in [100] axis, [11 0], [1 10] and [110] for the crystal pulled along [112] axis and [010] for [010] axis crystal.     

用FDTD与高分辨率谱估计相结合计算二维声子晶体的能带

基于现代信号处理中的高分辨率谱估计方法,对用时域有限差分方法计算二维声子晶体能带的迭代过程所输出的数据序列做后处理.数值仿真结果表明,相对于基于Fourier变换的后处理方法,该后处理方法在保证对二维声子晶体本征频率的精确估算的同时,能明显减少时域有限差分方法的迭代步数.     

耐等离子刻蚀陶瓷的研究现状

等离子刻蚀技术是超大规模集成电路制备工艺中不可或缺加工技术.在半导体晶圆尺寸不断增大以及特征尺寸不断缩少的发展进程中,晶圆的污染问题越来越突出.而刻蚀机腔室材料作为晶圆的主要污染源之一,其耐等离子刻蚀性日益受到人们的关注.本文主要介绍耐等离子体刻蚀腔体材料的特性及目前国内外的研究与发展现状.     

热交换法生长蓝宝石晶体的位错研究

本文用热交换法生长出a向,尺寸为φ150 mm×160 mm,重10 kg的低位错蓝宝石晶体,并采用化学腐蚀-金相显微镜法观测了(0001)晶面的位错形貌.结果显示:(0001)晶面的位错腐蚀坑呈三角形,分布较均匀和分散,图像清晰,平均位错密度较低,为2.1×103 Pits/cm2;热交换系统保温效果好,能独立控制熔体和晶体的温度梯度,温场起伏小,具有良好的稳定性和可控性,适合用来生长大直径低位错的蓝宝石晶体.     

CdGeAs2单晶体的腐蚀研究

报道了一种新型的CdGeAs2晶体择优腐蚀剂,配方为:H2O2(30;): NH4OH(含NH325;-28;): NH4Cl(5mol/L): H2O=1 mL: 1.5 mL: 1.5 mL: 2 mL.将经机械研磨、物理抛光和溴甲醇化学抛光处理后的表面平整无划痕的CdGeAs2晶片,在40 ℃下超声振荡腐蚀数分钟,采用金相显微镜和SEM进行蚀坑观察.结果表明,新型腐蚀剂对CdGeAs2晶体(204)和(112)晶面择优腐蚀效果显著,蚀坑取向一致,具有很强的立体感;(204)晶面蚀坑呈三角锥形,(112)晶面蚀坑呈五边形,从晶体结构上对蚀坑形成机理进行了分析讨论.     

Influence of Dislocations in KDP Crystals on Laser Damage Threshold

The dislocation density in KDP crystals has been determined by X-ray diffraction topography (LANG method). A method for determining the laser damage thresholds in dependence on dislocation density is described. It is found that dislocations with a density about 10³ cm⁻² reduce the laser damage threshold up to a factor of two compared with perfect regions. It is shown that experimentally measured damage results can be explained theoretically.     

湿法刻蚀机腔室关键结构及主要工艺参数对刻蚀性能的影响因素研究

以某18英寸湿法刻蚀机腔室为研究对象,建立了流-热耦合的数值分析模型,研究了刻蚀过程中工艺气体在圆筒式腔室内流速、压强、温度的分布规律,结合HF酸在乙醇环境下刻蚀SiO2的工艺原理,提出了由耗散系数、物质转换系数、物质量通量、品格结构等表征的刻蚀速率及刻蚀不均匀性评价方法,得到了腔室关键结构及主要工艺的参数对刻蚀性能的影响规律.     

Chemical Etching of Calcite Cleavages by Diluted Solutions

Very low concentration of mineral acids and monocarboxylic acid (less then 0.001%) produces triangular etch pits on calcite cleavages at dislocations intersecting the surface. The orienation of triangular etch pits is opposite with respect to percussion mark on calcite cleavages. This may be due to opposite process of percussion and reaction at very low concentrations. When percentage of water is slightly decreased in both above acids, rhombic etch pits were formed. The non-coincidence of depth points and geometerical centres of rhombic etch pits are explained. The similarity of shape cycle will not hold at higher concentrations.     

半导体碳化硅湿法腐蚀工艺研究

碳化硅(SiC)具有禁带宽度大、电子饱和漂移速度高、击穿场强高、热导率高、化学稳定性好等优异特性,是制备高性能功率器件等半导体器件的理想材料。得益于工艺简单、操作便捷、设备要求低等优点,湿法腐蚀已作为晶体缺陷分析、表面改性的常规工艺手段,应用到了SiC晶体生长和加工中的质量检测以及SiC器件制造。根据腐蚀机制不同,湿法腐蚀可以分为电化学腐蚀和化学腐蚀。本文综述了不同湿法腐蚀工艺的腐蚀机理、腐蚀装置和应用领域,并展望了SiC湿法腐蚀工艺的发展前景。